 
 (defn try-read-file [filename error-message]
   (try
-    (read-file filename)
+    (when filename
+      (read-file filename))
     (catch java.lang.RuntimeException re
       (is false
           (str "Contents of `" filename "'"

                              resource)]
    (if (resource-exists? resource-path)
      (io/resource resource-path)
      nil)))

(defn has-test-folder? []
  (some-> (site-test-folder)

               "at `resources/test/" site-name "/chapter_list.html'")))))

(defn test-extract-comic-list []
  (let [comic-test-resource (site-test-resource "comic_list.clj")
        {:keys [comic-list]}
        (try-read-file
         comic-test-resource
         "Please add a map with a :comic-list key.")]
    (if-let [html (comic-list-html)]
      (and
       (tu/ensure-dependencies-defined extract-comics-list)
       (is-defined-in-file comic-list comic-test-resource)
       (is (= comic-list
              (extract-comics-list html))
           (tu/display-dependent-data-values extract-comics-list)))
      (is false
